Central Dogma and Polio Flashcards
what are viruses?
obligate intracellular parasites
what are the 2 was viruses can use host resources / machinery?
- conform themselves to fit host machinery
2. conform host machinery to fit them
DNA dependent DNA polymerase uses ___ to make ___
dsDNA; more dsDNA
RNA polymerase uses ___ to make ___
dsDNA ; (+) ssRNA
ribosomes translate +ssRNA into ___
amino acid sequence
T/F virus genomes can be DNA or RNA
true
the genomes of viruses can be diverse, but all most pass through a stage that resembles ___
mRNA
why must all viruses go through a stage of resembling mRNA?
host protein synthesis can use it to make viral protein
gene products (mostly proteins) are required for what 5 things?
- replication of viral genome
- assembly and packaging of genome particles
- regulation and timing of replication cycle
- modulation of host defence
- spread to other cells and hosts
what information is encoded by viral genomes?
protein products
do viral genomes encode the complete protein synthesis machinery?
no
do viral genomes encode proteins involved in energy production and membrane synthesis? [
no
do viral genomes encode centromeres or telomeres?
no
+ ssRNA viruses get directly translated into the cytoplasm (T/F)
ture
how do polioviruses express their genes?
direct translation into cytoplasm
how do polioviruses replicate their genomes?
viral RNA dependent RNA polymerase with dsDNA intermediates
why don’t Polioviruses use host RNA dependent RNA polymerase?
because host cells don’t have them!
would progeny viruses be made if naked RNA into a host cell? Why/why not?
yes because the genome is already translated
the amino terminal makes a lot of ___ proteins
structural
the carboxyl terminal makes a lot of ___ proteins
enzymatic
T/F polyproteins can be cleaved by either host or viral proteases into the full complement of viral proteins
true
why do proteases make a good drug target? (2)
- if proteins are not made, the virus can’t replicate
2. unique (not going to accidentally target host)
disadvantage for virus relying on host proteases?
host is in control
poliovirus and HCV both encode RNA dependent RNA polymerase at which end of the genome?
3’
why is there an RNA dependent rna polymerase on the 3’ end of the polio genome?
it puts it in the perfect spot to bind to the rna and and start replication in the 5’ direction to make the complementary strand
T/F RDRP (rna dependent rna polymerase) is a drug target
true
the poliovirus causes what disease?
poliomyelitis
where does poliovirus live?
in the water
t/f the infection of poliomyelitis used to be common, but the infection was not
true
__% of cases of poliomyelitis are asymptomatic
95
__% of poliomyelitis cases spread to secondary tissues and cause flu-like symptoms
5
__% of poliomyelitis cases enter the central nervous system and results in selective destruction of motor neurone
less than 1
what are the 2 effective vaccines for poliomyelitis?
- sabin (oral)
2. stalk (intradermal)
how is the poliovirus grown and inactivated to make the stalk vaccine?
grown in kidneys of monkeys; inactivated by formalin
how is the poliovirus grown and attenuated in the sabin vaccine?
grown at subphysiologic temperatures, which causes the virus to undergo spontaneous mutations
t/f the attenuated poliovirus of the oral sabin vaccine can replicate in the gut
t
the oral Sabin vaccine establishes what type of immunity?
mucosal
what makes the erradication of poliomyelitis possible?
no animal reservoir
poliovirus binds to what receptor on the cell surface of a host?
CD155 (PVR)
what is the normal function of CD155 PVR?
cel-cell contact between epithelial cells
once bound to the PVR, how does the poliovirus enter the host cell?
endocytosis
once endocytized, the capsid of the poliovirus is ___ and releases __ into the cytoplasm
destabilized; +ssrna
what is the capsid shape of the poliovirus?
icosahedral
the icosohedral shape of the capsid of poliovirus allows it to survive __
the acidic pH of gut
the +ssrna of poliovirus is translated by __ to make a __
host ribosomes; polyprotein
viral and host proteases process polyprotein into ___ and __
capsid proteins and machinery for proteases and rna synthesis
t/f polyprotein translation if cotranslational
t
during polyprotein processing, as soon as viral protease is made, cleavage happens immediately, this is called __
auto proteolysis
auto proteolysis in processing poliovirus is due in part to __
viral enzymes acting in cis on the same molecule
__ is the viral rna dependent rna polymerase
3D
3d uses +ssrna as a template to make __ in the ___ direction
-ssrna; 3’-5’
3d makes a __ intermediate
ds rna
ds rna is the template for __
+ssrna progeny genome
in order to make +ssrna progeny from +rna, the rna polymerase first has to make the __
mirror image
what is a disadvantage of having an rna dependent polymerase?
sets off host recognition receptors
what is Ribavirin?
an inactive pro-drug which is phosphorylated and activated within cells
ribavirin is an analogue for __ and can therefore bind to
adenine and guanine ; cytosine, uracil
ribavirin induces ___ viruses, which can be lethal to rna viruses
hypermutation
t/f ribavirin can be incorporated into viral rna during genome replication
t